This invention concerns generally with pearlescent preparations and especially with cosmetics and relates to a process for the cold production of such preparations.
For centuries, the softly shimmering luster of pearls has held a particular fascination for human beings. It is therefore no wonder that manufacturers of cosmetic preparations, endeavour to give their products an attractive, valuable and rich appearance. The first pearlescence used in cosmetics in the middle ages was a pearlizing paste of natural fish scales. At the beginning of the present century, it was discovered that bismuth oxide chlorides were also capable of producing pearlescence. By contrast, pearlizing waxes, particularly of the glycol monofatty acid ester and difatty acid ester type, are of importance in modern cosmetics, being used mainly for the production of pearlescence in hair shampoos and shower gels. An overview of modern pearlizing formulations was published by A. Ansmann and R. Kawa in Parf. Kosm., 75, 578 (1994).
Various formulations capable of providing surface-active products with the required pearlescence are known from the prior art. For example, German patent applications DE 38 43 572 A1 and DE 41 03 551 A1 (Henkel) describe pearlizing concentrates in the form of free-flowing aqueous dispersions containing 15 to 40% by weight of pearlizing components, 5 to 55% by weight of emulsifiers and 0.1 to 5% by weight or 15 to 40% by weight of polyols. The pearlizing waxes are acylated polyalkylene glycols, monoalkanolamides, linear saturated fatty acids or ketosulfones. European patents EP 0 181 773 B1 and EP 0 285 389 B1 (Procter and Gamble) describe shampoo compositions containing surfactants, non-volatile silicones and pearlizing waxes. European patent application EP 0 205 922 A2 (Henkel) relates to free-flowing pearlizing concentrates containing 5 to 15% by weight of acylated polyglycols, 1 to 6% by weight of fatty acid monoethanolamides and 1 to 5% by weight of nonionic emulsifiers. According to the teaching of European patent EP 0 569 843 B1 (Hoechst), nonionic, free-flowing pearlizing dispersions can also be obtained by preparing mixtures of 5 to 30% by weight of acylated polyglycols and 0.1 to 20% by weight of selected nonionic surfactants. In addition, European patent application EP 0 581 193 A2 (Hoechst) describes free-flowing, preservative-free pearlizing dispersions containing acylated polyglycol ethers, betaines, anionic surfactants and glycerol. Finally, European patent application EP 0 684 302 A1 (Th. Goldschmidt) relates to the use of polyglycerol esters as crystallization aids for the production of pearlizing concentrates.
Commercially available pearlizing waxes have melting points above 80xc2x0 C. and, accordingly, cannot be incorporated cold into water-based formulations. Because of this, the expert has to use a hot process in which the waxes are melted and allowed to crystallize out slowly in the formulation, the particle fineness of the crystals and hence the brilliance of the pearlescence being a function of the cooling rate. Accordingly, it is immediately clear that hot processes are time-consuming and energy-intensive so that there is a need for a more favorable alterative. In general, therefore, the expert looks to so-called pearlizing concentrates which are more or less concentrated surfactant preparations which already contain the pearlizing waxes in fine-particle, i.e. pearlescent, form and which are stabilized by emulsifiers. Although pearlizing concentrates of the type in question can be further processed cold, the actual problem is not solved in this way and is merely passed onto to the manufacturer of these intermediate products because the concentrates in turn can of course only be obtained by a hot process.
Accordingly, the problem addressed by the present invention was to provide a process for the cold incorporation of pearlizing waxes in surfactant preparationsxe2x80x94whether intermediate products, such as pearlizing concentrates for example, or end formulations, such as shampoos for example. At the same time, neither the brilliance of the pearlescence nor the stability of the formulations would be adversely affected by the cold process.